Isolation contactor state control system

Abstract

A controller area network (CAN) installed on a hybrid electric vehicle provides one node with control of high voltage power distribution system isolation contactors and the capacity to energize a secondary electro-mechanical relay device. The output of the secondary relay provides a redundant and persistent backup signal to the output of the node. The secondary relay is relatively immune to CAN message traffic interruptions and, as a result, the high voltage isolation contactor(s) are less likely to transition open in the event that the intelligent output driver should fail.

What is claimed is: 
     
       1. A direct current power distribution system comprising:
 a low voltage direct current power source and an associated first low voltage bus for energization from the low voltage direct current power source; 
 a high voltage direct current power source and an associated high voltage bus for energization from the high voltage direct current power source; 
 a controller area network datalink; 
 a plurality of nodes connected to the controller area network datalink for exchanging data and further connected to the low voltage bus for energization; 
 an accessory relay responsive to a control input for connecting the first low voltage bus to the low voltage direct current power source; 
 a high side isolation contactor and a low side isolation contactor, the high and low side isolation contactors being responsive to control signals applied to control inputs for connecting the high voltage bus to the high voltage direct current power source and the low side isolation contactor to opposite polarity terminals of the high voltage direct current power source; 
 a supervisory sub-system for controlling energization of the low voltage bus and the high voltage bus by application of control signals to the control inputs of the accessory relay and to the low side and high side isolation contactors and further connected to the controller area network datalink for exchanging data with the plurality of nodes; and 
 an external state select switch connected to the supervisory sub-system for requesting changes in state of the low voltage bus and the high voltage bus; 
 a second low voltage bus for energization to at least the control signal level for the high and low side isolation contactors, the second low voltage bus being connected to the control input of the high side isolation contactor and energized from the low voltage direct current power source in response to closure of the high side isolation contactor. 
 
     
     
       2. The direct current power distribution system of  claim 1 , further comprising:
 a latch relay for connecting the second low voltage bus to the low voltage direct current power supply. 
 
     
     
       3. The direct current power distribution system of  claim 2 , further comprising:
 the latch relay having a control input connected to the second low voltage bus and to its own power output terminal; and 
 a break latch relay for providing a connection between the control coil of the latch relay and ground. 
 
     
     
       4. The direct current power distribution system of  claim 3 , further comprising:
 a pre-charge isolation contactor connected in parallel with the high side isolation contactor, the pre-charge isolation contactor being controlled by control signals generated by the supervisory sub-system. 
 
     
     
       5. The direct current power distribution system of  claim 3 , further comprising:
 the control input to the accessory relay being connected to the second low voltage bus. 
 
     
     
       6. The direct current power distribution system of  claim 5 , further comprising:
 the connections from the second low power bus to the control inputs for the low side isolation contactor and the accessory relay including diodes oriented to forward conduct in the direction of the control inputs. 
 
     
     
       7. The direct current power distribution system of  claim 5 , further comprising:
 a service stop relay for connecting the control coils of the low side isolation contactor, the high side isolation contactor and the pre-charge isolation contactor to ground. 
 
     
     
       8. A control system for an electric or hybrid-electric vehicle electrical power distribution system comprises:
 at least first and second power distribution buses; 
 first and second power connection elements for connecting the first and second power distribution buses to sources of direct current power, the first and second power connection elements including control input terminals; 
 a supervisory sub-system responsive to exogenous inputs for generating first and second control signals for application to the control input terminals; 
 a latch relay having a control input tied to receive the second control signal and responsive to its presence for connecting its control input substantially directly to a power source; and 
 the latch relay being connected by a forward conducting diode to the control input terminal for the first power connection element. 
 
     
     
       9. The control system of  claim 8 , further comprising:
 a break latch relay connected between the latch relay and ground to allow release of the latch relay from of self locked condition. 
 
     
     
       10. The control system of  claim 9 , further comprising:
 the second power connection element including a high side isolation contactor and a low side isolation contactor with the high side isolation contactor having a control input directly tied to the control input for the latch relay and the control input for the latch relay being connected by uni-directional current element to a control input for the low side isolation contactor. 
 
     
     
       11. The control system of  claim 9 , further comprising:
 the first power connection including an accessory relay and a service stop relay, both relays having control inputs connected to the control input terminal for the latch relay by unidirectional current elements.